The Display settings menu looks somewhat like this: However, when I connect my Macbook to a 2K monitor, the Scaled option is not available, I can only set the resolution.
The best thing here is the Scaled option, which means that I can use the native resolution of the screen and rescale all UI elements bigger or smaller depending on my taste and they still look very sharp. When I use my Macbook Pro's internal monitor, I have the following options in the Display settings menu:
